Industrialist Stéphane is getting a bit long in the tooth, but is still an incredibly charming man. When his wife Sophie goes away for the Easter weekend, he meets the attractive Julie by chance. The old philanderer takes her home with him to seduce the young lady. Due to an unforeseen strike, his wife Sophie is unable to fly out as planned and suddenly appears on the scene. Out of necessity, Stéphane unceremoniously introduces Julie as his daughter...

Commissioner Brockmann's criminal investigation is prompted by the body found by the cleaner Erna Pieper, which turns out to be very mobile! She disappears and reappears, causing considerable confusion among the survivors. The inspector and the cleaner get into a fierce competition to solve the case. The expert and the naively clever dilettante engage in a veritable battle of applied detective story logic. Which professionally proud expert likes it when a "little woman from the street" keeps messing up his work with her uneducated, "common sense" - and is successful at the same time...